Edge influence on plant litter biomass in forest and savanna in the Brazilian cerrado

Edge influence, characterized by differences in ecosystem characteristics between the edge and the interior of remnants in fragmented landscapes, affects a variety of organisms and ecosystem processes. An important feature that may be affected by edges is the amount of plant litter, which provides important habitat for a large variety of organisms and influences ecological processes such as fire dynamics. We studied edge influence on plant litter and fine woody debris in the cerrado of São Paulo state, south‐eastern Brazil. We collected, sorted, dried and weighed plant litter along 180 m‐long transects perpendicular to three savanna and eleven forest edges adjacent to different anthropogenic land uses, with four to five transect per edge. There tended to be less biomass of the finer portions of fine woody debris at both savanna and forest edges. Graminoid litter at savanna edges was greater than in the corresponding interior areas, whereas other litter portions were either unaffected by edges or did not show consistent patterns in either savanna or forest. Edge influence was usually restricted to the first 20 m from the edge, was not influenced by edge characteristics and exhibited no clear differences between savanna and forest areas. Several mechanisms may have led to the variable patterns observed including variation in the plant community, plant architecture, and invasive species. The edge‐related variation in plant litter may putatively lead to, for example, increased fire frequency and intensity at the savanna edges and altered trophic dynamics at forest edges; the mechanisms and consequences of this edge influence should be addressed in future studies.     

Altered leaf-litter decomposition rates in tropical forest fragments

The effects of forest fragmentation on leaf-litter decomposition rates were investigated for the first time in an experimentally fragmented tropical forest landscape in Central Amazonia. Leaf-litter decomposition rates were measured at seven distances (0–420 m) along forest edge-to-interior transects in two 100-ha fragments, two continuous forest edges, and at an identical series of distances along two deep continuous forest transects, as well as at the centers of two 1-ha and two 10-ha fragments. Decomposition rates increased significantly towards the edge of 100-ha forest fragments. Litter turnover times were 3–4 times faster within 50 m of the edge of 100-ha fragments than normally found in deep continuous forest. In contrast, there was no significant change in the rate of leaf-litter decomposition from the interior to the edge of continuous forest. It is difficult to account for these very different edge responses. Decomposition rates were not correlated with air temperature differentials, evaporative drying rates, litter depth, biomass or moisture content, or with total invertebrate densities, either within individual edge transects or across all sites. The difference in edge response may be due to chance, particularly the patchy removal of vast quantities of litter by litter-feeding termites, or may be a real, area-dependent phenomenon. Clearly, however, forest fragmentation increases the variability and unpredictability of litter decomposition rates near forest edges. In addition to edge effects, decomposition rates were strongly affected by decreasing fragment area. While sites at the centers of 10-ha and 100-ha forest fragments and continuous forest had equivalent decomposition rates, rates were markedly lower at the centers of 1-ha fragments. Litter turnover times were 2–3 times slower in 1-ha fragments than in continuous forest, and up to 13 times slower than at 100-ha edges. Litter structure and nutrient cycling dynamics are inevitably altered by forest fragmentation. Received: 16 October 1997 / Accepted: 14 April 1998     

The role of edge contrast and forest structure in edge influence: vegetation and microclimate at edges in the Brazilian cerrado

The effect of the adjacent non-forested environment on the forest near the edge, edge influence (EI), is an important impact in fragmented landscapes and is believed to vary with factors such as forest structure and edge contrast. In order to improve our understanding of the factors governing the variability in EI, we studied microclimate and vegetation at cerrado edges surrounded by variable land uses in southeastern Brazil, a system with both forest and savanna fragments. We determined the significance, magnitude and distance of EI on microclimate, vegetation structure and grass biomass which we measured along five transects perpendicular to fourteen edges in forest or savanna next to different land uses. We introduce a quantitative measure of edge contrast that considers land uses at different distances from the same edge (e.g., a firebreak between a forest edge and a plantation) and verified whether edge contrast is correlated with EI in this system. Notwithstanding the large variation in EI among variables and study sites, there were some similarities in the patterns of EI between forest and savanna edges. Edge contrast was successfully quantified by our measure but was only correlated with EI on moisture and grass biomass. Our results point to the high variability in EI within a region. Our quantitative measure of edge contrast may be useful in explaining variability in EI. However, much unexplained variation remains in the highly fragmented cerrado system which is affected by EI in both forest and savanna fragments.     

Tree Regeneration and Understory Woody Plants Show Diverse Responses to Forest–Pasture Edges in Costa Rica

ABSTRACT Edge effects along tropical forest–pasture margins are thought to cause a shift toward early successional characteristics of the understory forest vegetation. We tested this idea by sampling vegetation at five forest sites in northeast Costa Rica each of which had edges that were established over 20 yr earlier. Four of these sites had been selectively logged. We sampled woody plants >0.2 and ≤1.3 m height in 54 m² within 0.2 ha plots at edges (N=14), and at 150 m (N=11) and 300 m from edges (N=9). Composition and diversity did not vary with edge distance. Abundance of tree regeneration, mainly of canopy and emergent species, increased at edges. Abundance of lianas and slow‐growing tree species did not differ significantly across the sampling locations. Weighted mean wood density varied little, with a reduction at edges for canopy species. Palms were less abundant at edges, but not less species rich. At edges, these plant assemblages maintain many of the characteristics of forest interior vegetation, though the changes observed may indicate ongoing functional change. Degradation of forest–pasture edges is not a universal feature of tropical forest fragmentation, and forests with high rates of natural turnover might have a high capacity to maintain themselves within forest edges alongside pasture.     

Influence of habitat,litter type,and soil invertebrates on leaf-litter decomposition in a fragmented Amazonian landscape

Amazonian forest fragments and second-growth forests often differ substantially from undisturbed forests in their microclimate, plant-species composition, and soil fauna. To determine if these changes could affect litter decomposition, we quantified the mass loss of two contrasting leaf-litter mixtures, in the presence or absence of soil macroinvertebrates, and in three forest habitats. Leaf-litter decomposition rates in second-growth forests (>10 years old) and in fragment edges (<100 m from the edge) did not differ from that in the forest interior (>250 m from the edges of primary forests). In all three habitats, experimental exclusion of soil invertebrates resulted in slower decomposition rates. Faunal-exclosure effects were stronger for litter of the primary forest, composed mostly of leaves of old-growth trees, than for litter of second-growth forests, which was dominated by leaves of successional species. The latter had a significantly lower initial concentration of N, higher C:N and lignin:N ratios, and decomposed at a slower rate than did litter from forest interiors. Our results indicate that land-cover changes in Amazonia affect decomposition mainly through changes in plant species composition, which in turn affect litter quality. Similar effects may occur on fragment edges, particularly on very disturbed edges, where successional trees become dominant. The drier microclimatic conditions in fragment edges and second-growth forests (>10 years old) did not appear to inhibit decomposition. Finally, although soil invertebrates play a key role in leaf-litter decomposition, we found no evidence that differences in the abundance, species richness, or species composition of invertebrates between disturbed and undisturbed forests significantly altered decomposition rates.     

Species traits and the response of open‐habitat species to forest edge in landscape mosaics

Human driven changes in land‐use have increased the need to understand how landscape structure affects species distribution. We studied how forest edges affected the distribution of birds in grasslands recently encroached by forest patches. We investigated how species’ biological traits influenced their response to vegetation change near forest edges. We censured birds along 300‐m line transects run into the open habitat perpendicularly to forest edges. We recorded habitat variables and landscape context along each transect and characterized edges and forest patches. We recorded 33 bird species in 153 transects for a total of 654 individuals. We analyzed species response to edges with generalized linear mixed models. Habitat preference was prevalent to explain species response to forest edges. The abundance of open‐habitat birds such as skylark Alauda arvensis decreased significantly in the vicinity of edges. This negative response extended within 150 m from the edge. The effect was disproportionately higher in open‐habitat species with high conservation concern. The abundance of species feeding or/and breeding in both forest and open habitat, such as woodlarks Lullula arborea, sharply increased near edges (positive edge response). Abundance of shrub and non‐shrub dependent species increased with distance to edge. The two species groups did no differ in abundance/distance to edge relationship. Intensity of species response to forest edges varied among transects in relation to transect vegetation characteristics. Edge length or aspect, diet and nest height had no direct effect. We discuss the possible role of variation in resources and nest predation risk to explain observed patterns.     

Discriminating the Drivers of Edge Effects on Nest Predation: Forest Edges Reduce Capture Rates of Ship Rats (Rattus rattus), a Globally Invasive Nest Predator,by Altering Vegetation Structure

Forest edges can strongly affect avian nest success by altering nest predation rates, but this relationship is inconsistent and context dependent. There is a need for researchers to improve the predictability of edge effects on nest predation rates by examining the mechanisms driving their occurrence and variability. In this study, we examined how the capture rates of ship rats, an invasive nest predator responsible for avian declines globally, varied with distance from the forest edge within forest fragments in a pastoral landscape in New Zealand. We hypothesised that forest edges would affect capture rates by altering vegetation structure within fragments, and that the strength of edge effects would depend on whether fragments were grazed by livestock. We measured vegetation structure and rat capture rates at 488 locations ranging from 0–212 m from the forest edge in 15 forest fragments, seven of which were grazed. Contrary to the vast majority of previous studies of edge effects on nest predation, ship rat capture rates increased with increasing distance from the forest edge. For grazed fragments, capture rates were estimated to be 78% lower at the forest edge than 118 m into the forest interior (the farthest distance for grazed fragments). This relationship was similar for ungrazed fragments, with capture rates estimated to be 51% lower at the forest edge than 118 m into the forest interior. A subsequent path analysis suggested that these ‘reverse’ edge effects were largely or entirely mediated by changes in vegetation structure, implying that edge effects on ship rats can be predicted from the response of vegetation structure to forest edges. We suggest the occurrence, strength, and direction of edge effects on nest predation rates may depend on edge-driven changes in local habitat when the dominant predator is primarily restricted to forest patches.     

Do edge effects increase the susceptibility of rainforest fragments to structural damage resulting from a severe tropical cyclone?

Abstract If changes in the structural characteristics of rainforest at edges are caused by wind, then physical damage from a tropical cyclone might be greatest at edges or in small fragments that have a high proportion of edge. We tested whether this was true of a fragmented rainforest landscape impacted by a category 4 severe tropical cyclone in March 2006. Six structural variables (canopy cover, canopy height, cover of ground vegetation, leaf litter, stem density and counts of woody debris) were surveyed at 18 rainforest sites (six small linear remnants, and both edges and interiors of six large remnants) on the Atherton Tableland in north‐eastern Queensland, Australia. Data collected 7 and 12 months after the passage of Cyclone Larry were compared with an identical survey conducted 4 years prior to the cyclone. The cyclone had large effects across many components of forest structure. However, sites within 30 m of forest edges in small and large remnants were not impacted more than the interiors of large remnants. It is likely that the high wind intensity from severe tropical cyclones overrides the modest wind protection provided by surrounding forest. The cyclone's effects were highly patchy at local scales (0.5–1.0 km), leading to an increase in among‐site variation in forest structure and the disappearance of significant spatial autocorrelation among large remnant edge‐interior site pairs which had existed prior to the cyclone. The main effect of Cyclone Larry at these study sites was to increase the spatial heterogeneity of forest structure at local scales.     

High density of white-faced capuchins (Cebus capucinus) and habitat quality in the Taboga Forest of Costa Rica

Across the globe, primates are threatened by human activities. This is especially true for species found in tropical dry forests, which remain largely unprotected. Our ability to predict primate abundance in the face of human activity depends on different species' sensitivities as well as on the characteristics of the forest itself. We studied plant and primate distribution and abundance in the Taboga Forest, a 516-ha tropical dry forest surrounded by agricultural fields in northwestern Costa Rica. We found that the density of white-faced capuchins (Cebus capucinus) at Taboga is 2–6 times higher than reported for other long-term white-faced capuchin sites. Using plant transects, we also found relatively high species richness, diversity, and equitability compared with other tropical dry forests. Edge transects (i.e., within 100 m from the forest boundary) differed from interior transects in two ways: (a) tree species associated with dry forest succession were well-established in the edge and (b) canopy cover in the edge was maintained year-round, while the interior forest was deciduous. Sighting rates for capuchins were higher near water sources but did not vary between the edge and interior forest. For comparison, we also found the same to be true for the only other primate in the Taboga Forest, mantled howler monkeys (Alouatta palliata). Year-round access to water might explain why some primate species can flourish even alongside anthropogenic disturbance. Forest fragments like Taboga may support high densities of some species because they provide a mosaic of habitats and key resources that buffer adverse ecological conditions.     

The Seedling Community of Tropical Rain Forest Edges and Its Interaction with Herbivores and Pathogens1

Edge effects alter biotic interactions and forest regeneration. We investigated whether edge creation affected the seedling community and its interactions with herbivores and leaf‐fungal pathogens. In forest edges and interior sites in Chiapas, Mexico, we counted all woody seedlings and species (10–100 cm tall) present in 1‐m² plots, measured their size (height and leaf number), and examined them for the occurrence of herbivory and pathogen damage. We investigated relationships between levels of damage and size, species richness and density. Species composition and biotic damage varied greatly among sites and habitats (edge vs interior). Late‐successional species dominated the community, but richness was lower in interior sites and species similarity was greater among edges than among interiors. Nearly all species (95%) present at edges and interiors showed herbivory damage, whereas 76 percent of the species in edge plots and 68 percent in interior plots showed pathogen damage. Although leaf area damaged by herbivores was similar between habitats (average 9.2%), pathogen damage was three times greater in edge plots (1.85%) than in interior plots (0.57%). Size was positively related to biotic damage at both habitats. Relationships between herbivory and pathogen damage and between pathogen damage and leaf number were significant only for edges. Biotic damage was not related to density or species richness. Overall, plant community structure was similar between habitats, but biotic damage was enhanced at edges. Thus, disease spread at edges may arise as a threat to tropical rain forest vegetation.     

Contrasting Demographic Structure of Short‐ and Long‐lived Pioneer Tree Species on Amazonian Forest Edges

Although tropical forests have been rapidly converted into human‐modified landscapes, tree species response to forest edges remains poorly examined. In this study, we addressed four pioneer tree species to document demographic shifts experienced by this key ecological group and make inferences about pioneer response to forest edges. All individuals with dbh ≥ 1 cm of two short‐lived (Bellucia grossularioides and Cecropia sciadophylla) and two long‐lived species (Goupia glabra and Laetia procera) were sampled in 20 1‐ha forest edge plots and 20 1‐ha forest interior plots in Oiapoque and Manaus, Northeast and Central Amazon, respectively. As expected, pioneer stem density with dbh ≥ 1 cm increased by around 10–17‐fold along forest edges regardless of species, lifespan, and study site. Edge populations of long‐lived pioneers presented 84–94 percent of their individuals in sapling/subadult size classes, whereas edge populations of short‐lived pioneers showed 56–97 percent of their individuals in adult size classes. These demographic biases were associated with negative and positive net adult recruitment of long‐ and short‐lived pioneers, respectively. Our population‐level analyses support three general statements: (1) native pioneer tree species proliferate along forest edges (i.e., increased density), at least in terms of non‐reproductive individuals; (2) pioneer response to edge establishment is not homogeneous as species differ in terms of demographic structure and net adult recruitment; and (3) some pioneer species, particularly long‐lived ones, may experience population decline due to adult sensitivity to edge‐affected habitats.     

Buffering of native forest edge microclimate by adjoining tree plantations

Abstract In the Waikato Region of New Zealand, Pinus radiata (D. Don) plantations are becoming increasingly common on land adjacent to native forest fragments. It is unclear whether this juxtaposition is beneficial or detrimental to native forest fragment quality and persistence. We hypothesized that adjacent dense plantations buffer native fragments from microclimatic exposure, reducing edge effects and expanding the area of interior‐like native forest. Microclimate parameters were measured in native forest fragments adjacent to grazed pasture (‘abrupt’ edges) and in fragments adjacent to mature P. radiata plantations (‘embedded’ edges) during late summer. Photosynthetically active radiation, air temperature and vapour pressure deficit (VPD) were measured along transects perpendicular to edges during the mid‐afternoon, when gradients were typically steady and maximal, to investigate spatial variation. At paired abrupt versus embedded edges these same variables were monitored for week‐long periods to determine temporal variation. In fragments adjacent to pasture, conditions were significantly lighter and warmer (but not drier) than the interior along transects at distances up to 20 m from the edge. In contrast, no variables differed significantly along transects adjacent to pine. The different microclimate variables measured at edges (except VPD) contributed to edge effects at different times through a daily cycle. Photosynthetically active radiation was significantly different between abrupt and embedded edges at all times of the day. Air temperature was significantly different during mid‐day and afternoon, but not during the morning nor at night. Vapour pressure deficit varied considerably over time and between sites, but was never consistently higher at one type of edge. We conclude that pine plantations in the Waikato Region provide valuable microclimate buffering during the day, principally due to their effect in reducing light and temperature to interior‐like conditions at native forest edges. Consequently, plantations are a compatible neighbouring land use to forest fragments. Such buffering could be extended through the pine harvesting‐replanting phase with appropriate management, such as leaving an undisturbed margin during harvest.     

Driving Factors Behind Litter Decomposition and Nutrient Release at Temperate Forest Edges

Forest edges have become important features in landscapes worldwide. Edges are exposed to a different microclimate and higher atmospheric nitrogen (N) deposition compared to forest interiors. It is, however, unclear how microclimate and elevated N deposition affect nutrient cycling at forest edges. We studied litter decomposition and release of N, phosphorus (P), total cations (TC) and C/N ratios during 18 months via the litterbag technique along edge-to-interior transects in two oak (Quercus robur L.) and two pine (Pinus nigra ssp. laricio Maire and ssp. nigra Arnold) stands in Belgium. Furthermore, the roles of edge conditions (microclimate, atmospheric deposition, soil fauna and soil physicochemical conditions), litter quality and edge decomposer community were investigated as underlying driving factors for litter decomposition. Litter of edge and interior was interchanged (focusing on the influence of edge conditions and litter quality) and placed in open-top chamber (OTC), which create an edge (warmer) microclimate. As the decomposer macrofauna was more abundant at the edge than in the interior, the OTCs were used to isolate the effects of warming versus soil fauna. Oak litter at the edge lost 87 and 37% more mass than litter in the interior. We demonstrated an edge effect on litter decomposition and nutrient release, caused by an interplay of edge conditions (atmospheric deposition of N and TC, soil pH and C/N ratio), litter quality and soil fauna. Consequently, edge effects must be accounted for when quantifying ecosystem processes, such as litter decomposition and nutrient cycling in fragmented landscapes.     

Dirt roads and fire breaks produce no edge effects on litter-dwelling arthropods in a tropical dry-forest: a case study

Edge effects threaten organisms and ecological processes in habitat remnants, but they have been poorly studied in non-humid forests such as cerradão, a tropical dry forest sometimes derived from fire-suppressed savanna in Brazil. The diverse ecosystem functions performed by arthropods may be disrupted by edge effects, and there is pressing need for more studies on this subject. We sampled fragments of cerradão facing either a road or fire breaks, assessing edge effects in: beta diversity and community composition of epigaeic (litter-dwelling) arthropod orders, ant species, and ant functional groups; ant species richness and diversity; leaf litter depth; and colony residence time of a predatory ground-dwelling ant, Odontomachus chelifer (Ponerinae). None of the variables measured differed between edge and interior of the sites sampled. Dry forests have high micro-climatic variations caused by discontinuities in the canopy cover and, as such, changes in abiotic variables in cerradão edges might not be as clear as those observed in tropical rainforests. Our study demonstrates that edge effects may not be so prevalent in cerradão facing roads or fire breaks, which possibly increases the chances of survival of a higher fraction of the original arthropod fauna compared to rainforest fragments.     

Edge effects decrease ant-derived benefits to seedlings in a neotropical savanna

Edge effects may lead to changes in mutualistic plant–animal interactions, such as seed dispersal, that are critical to plant regeneration. However, research into edge effects is neglected in the Brazilian cerrado, the largest neotropical savanna. We evaluated the consequences of edge effects in the cerrado for the regeneration of Erythroxylum pelleterianum (Erythroxylaceae), a shrub that benefits from seed dispersal by ants. We compared air temperature, relative humidity, and vapor pressure deficit, as well as the frequency and outcome of ant–diaspore interactions between cerrado edges and interiors. The inner portion of cerrado was likely to be moister than its borders, but seed production and germination did not differ between edge and interior of cerrado. Ants removed more seeds near fragment edges than at the interior. However, Myrmicinae ants dominated ant–fruit interactions at edges. These ants are likely to provide few benefits to the seeds. Seedlings of E. pelleterianum growing close to Ponerinae ant nests showed higher survival than seedlings growing away from nests in the interior of cerrado, but such effect disappeared near edges. Widespread seedling mortality due to a higher evaporative demand at edges may partially account for this effect. Furthermore, Ponerinae’s nests also showed a lower residence time near edges, decreasing possible benefits derived from ant colony activity such as nutrient enrichment and protection against insect herbivores. Edge effects could change the structure and dynamics of vegetation in cerrado fragments, due in part to the collapse of the mutualistic interactions demonstrated here.     

Viability of ecological processes in small Afromontane forest patches in South Africa

Abstract The conservation of biodiversity is dependent on protecting ecosystem‐level processes. We investigated the effects of fragment size and habitat edge on the relative functioning of three ecological processes – decomposition, predation and regeneration of trees – in small Afromontane forests in KwaZulu‐Natal, South Africa. Ten sampling stations were placed in each of four forest categories: the interior of three large indigenous forest fragments (100 m from the edge), the edges of these large fragments, 10 small indigenous fragments (<1 ha) and 10 small exotic woodlands (<0.5 ha). Fragment size and edge effects did not affect the abundance of the amphipod Talitriator africana, a litter decomposer, and overall dung beetle abundance and species richness significantly. Bird egg predation was marginally greater at large patch edges compared with the other forest categories, while seed predation did not differ among forest categories. Tree seedling assemblage composition did not differ significantly among large patch interiors and edges, and small indigenous fragments. Sapling and canopy assemblage composition each differed significantly among these three indigenous forest categories. Thus, while tree recruitment was not negatively affected by patch size or distance from the edge, conditions in small fragments and at edges appear to affect the composition of advanced tree regeneration. These ecological processes in Afromontane forests appear to be resilient to fragmentation effects. We speculate that this is because the organisms in these forests have evolved under fragmented conditions. Repeated extreme changes in climate and vegetation over the Pleistocene have acted as significant distribution and ecological extinction filters on these southern hemisphere forest biota, resulting in fauna and flora that are potentially resilient to contemporary fragmentation effects. We argue that because small patches and habitat edges appear to be ecologically viable they should be included in future conservation decisions.     

Forest edges and habitat selection in birds: a functional approach

Edge effects encompass a complex panoply of biotic and biotic phenomena across woodlan borders. I identify four main explanations which have been proposed to explain avian habital selection with respect to forest edges: 1) individualistic resource and patch use. 2) biotic interactions: 3) microclimate modification 4) changes in vegetation structure. In relates nest site location in woodlands relative to the edge to the proximity of food resources. It is shown that all other things being equal birds which are wholly dependent on resources found within woodlands will tend to avid forest edges. Woodland species dependent upon resources found in adjacent habitats will tend to be found near to edges to enable their exploitation. 2) identifies competition predation and brood parasitism as factor which have the potential to influence bird habitat selection near edges. 3) identifies microclimate modification as a potential influence which may are directly on nesting success or indirectly through its effects on food supply: 4) relates the activities of birds such as nesting feeding or Research on edge effects of birds in woodland has provided few practical recommendations to conservation managers. Forest edge management needs to take into account the multiple cause and defects which influence habitat selection at the edge and to target species of conservation concern.     

Distributions of lizard species across edges delimiting open‐forest and sand‐mined areas

Abstract The distributions of lizards across habitat edges delimiting open‐forest and regenerating sand‐mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall‐trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine‐path to the forest so that it was identified as a mine‐path specialist lizard species. Captures of two skink species decreased across the mine‐path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine‐path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open‐forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.     

Influence of Edge Exposure on Tree Seedling Species Recruitment in Tropical Rain Forest Fragments1

Edge creation has a pronounced influence on the understory vegetation, but the effects of edges on seedling species recruitment are still poorly understood. In Central Amazonia, 9–19 years after fragmentation, we recorded species richness and net seedling recruitment rate in 1 ha blocks exposed to none, one, or multiple edges within forest fragments. One‐hectare blocks were located in the center (no edge), the edge (one edge), the corners (two edges) of 10 and 100 ha fragments, and in a 1 ha fragment (four edges). In 1991, we counted all tree seedlings 5–100 cm tall found within permanent 1 m² plots located within the 1 ha blocks. In May 1993, we manually removed all seedlings that were smaller than 1 m tall from the permanent plots. Six years and five months later (October 1999), all new seedlings recruited into the plots were counted and classified into distinct morphospecies. Species richness of recruited seedlings, scaled by total seedling density, declined from the center to the edge, the corner blocks, and then to the 1 ha fragment. Overall, the four‐edged, 1 ha fragment had the poorest species richness and the non‐edged 100 ha central block the highest. The total number of recruited individuals was 40 percent less than that previously present, with the 100 ha corner having the lowest recruitment. Pairwise comparisons showed that species similarity was related to edge number for the 100 and 1 ha fragments. Species rank/abundance curves showed that a subset of species was common in all blocks within the fragments, and that the 100 ha center held more rare species than any other 1 ha block. This study demonstrated that, in a given fragment patch, the number of tree seedling species recruited varied inversely with the number of edges.     

Ground-dwelling spiders (Arachnida, Araneae) in fragmented old forests and surrounding managed forests in southern Finland

We studied the structure of spider assemblages in fragments of old coniferous forest in the southern Finnish taiga We sampled spiders with pitfall traps in the interiors and in the edges of the old-forest patches and in the surrounding managed forests We surveyed assemblages of ground-dwelling spiders and the relation of species to formerly mentioned three forest-habitat categories We analysed spider assemblages in relation to vegetation structure as well As in forest spiders there are no habitat specialists, no strict old-forest species were found However, the spider assemblages of old forests were different from those in the surrounding managed forests The difference was attributable to habitat differences, mainly to reduced tree-canopy cover in managed forests Large hunting-spider species (Gnaphosidae, Lycosidae) benefitted from clearcutting and other management measures, whereas the catches of small forest-living species (Linyphiidae) decreased in plantations and open forests The hunters colonized the edges of old-forest fragments, and were seldom found in the interior of old forest Size of old-forest fragment did not affect significantly the spider assemblage The results indicate that a buffer zone of mature forest with closed canopy should be left to surround the old-growth reserves in order to minimize the edge effect in the fragments